1. Field of the Invention
This invention relates to petroleum additive compositions, particularly to compositions which are in particulate form, water insoluble and characterized by slow, controlled oil-solubility at high temperatures and pourability at low temperatures. The invention especially relates to water insoluble, particulate compositions comprising petroleum additives, such as pour point depressants, paraffin inhibitors, corrosion inhibitors, biocides and the like, which compositions are slowly and controllably soluble in petroleum systems at elevated temperatures. The invention further relates to methods of inhibiting paraffin deposition, corrosion, rust, and bacterial and algal growth and a method of reducing the pour point of petroleum systems by virtue of incorporating therein the above-described compositions.
It is known that crude oils and heavier petroleum fractions, such as residual fuel oils, often contain substantial quantities of waxy materials. When such oils are subjected to temperatures below their cloud points, the waxy constituents tend to deposit on cool surfaces or crystallize and agglomerate into a solid gel. The gelling or stiffening of the oil introduces rheological problems which interfere with normal oil production and cause handling problems. High viscosities and high pour points result in additional production costs, such as increased horsepower, increased equipment size and increased fuel usage to heat the crude. Particularly affected by such rheological problems are long distance pipelines and offshore production facilities.
In addition to higher viscosities resulting from the gelling of petroleum, as described above, certain waxy fractions in crude oil may actually deposit directly on cold surfaces as the crude is exposed to cooler temperatures during production. The decrease in solubility of the waxy fraction with decreasing temperature results in wax deposits which reduce the volume of oil which can be produced. The addition of paraffin inhibitors helps to resolve wax deposition, but one of the greatest problems related to the use of paraffin inhibitors in most oilfield environments is the poor physical properties associated with these high molecular weight materials. Most effective treatment chemicals are either high melting solids or high pour point liquids or gells which pose a variety of handling problems in low temperature environments. The solids are handleable at ambient surface temperatures but dissolve too rapidly at high down-hole temperatures. The high molecular weight liquids frequently gel at ambient surface temperatures of 4.degree.-10.degree. C. or below and must be heated or diluted to be useful. Heated storage at the wellhead or dilution with solvents is normally required to allow continuous injection. Normal dilution may require as much as 95 to 98% solvent in order to achieve adequate application of paraffin inhibitor.
In view of the aforementioned problems, an object of the present invention is to provide compositions and methods for treatment of high temperature petroleum systems (i.e. down-hole) whereby the active ingredients of the composition do not immediately dissolve in the petroleum system but, instead, are gradually released over a period of time. At the same time, the compositions of the invention are particulate solids which are pourable at low ambient surface temperatures.
A further object is to provide paraffin inhibitor compositions and methods for treating high temperature petroleum systems.
Another object is to provide pour point depressant compositions and methods for treating high temperature petroleum systems.